A typical ZIF connector comprises an insulating housing having a trough-like recess into which the edge portions of a panel-like member, such as a circuit board, are inserted. The housing contains a plurality of contact terminals which have contact portions that engage conductors on the circuit board. A ZIF connector differs from a non-ZIF connector in that the ZIF connector has a cam or other device by means of which the terminals can be flexed or moved to positions such that they do not extend into the recess. The circuit board can thus be inserted into the connector under zero insertion force conditions. ZIF connectors are desirable for several reasons; the circuit board can obviously be inserted into the recess more easily under ZIF conditions than under circumstances where the circuit board must be pushed between the contact portions of the terminals in the housing. Additionally, when the circuit board is inserted into a non-ZIF connector, the contact portions of the terminals must slide over the conductors on the circuit board for a short distance and if the terminals are designed to exert high contact forces, the plating on the circuit board conductors will be damaged.
Known types of ZIF connectors usually have a cam that moves the terminals towards or away from the recess in the connector housing located relatively close to the fulcrum locations of the terminals, that is, close to the locations at which the terminals are fixed to the connector housing. The cam thus engages the terminal at the end of a fairly short lever arm and since the end portion of the terminal in which the contact is provided must be moved, a relatively high force may be required to move the cam. The force required to actuate the cam becomes excessively high if the connector contains a relatively large number of terminals, say 300 to 500 terminals, and if each terminal is designed to develop a contact force in excess of 125 grams. It is quite common to provide terminals in some connectors which develop contact force of 200 or more grams per terminal and it can readily be seen that a substantial force will be required to move the cam in a manner which will flex all of the terminals in the connector. These problems in the design of ZIF connectors become increasingly troublesome if the connector must be of reduced size and must have its contact terminals on closely spaced centers, for example, 1.27 mm. The present invention is directed to the achievement of ZIF connectors having improved terminals and cams which are such that the cams can be actuated by the application of a relatively low rotary or linear force to the cams, even when the connector contains a relatively large number of contact terminals.
A ZIF multi-contact electrical connector in accordance with the invention comprises an insulating housing having oppositely facing first and second major surfaces, oppositely facing endwalls, and oppositely facing sidewalls. The first major surface has a trough-like recess therein extending parallel to the sidewalls for reception of the edge portions of a panel-like member such as a circuit board. A plurality of side-by-side terminal receiving cavities are provided in the housing on each side of the recess and a contact terminal is positioned in each cavity. The terminals extend substantially to the second major surface and have contact portions which are proximate to the recess for contacting the conductors on the panel-like member. A camming rod or a pair of camming rods, extend through the connector housing and engage the terminals thereby to cause movement of the contact portions towards and away from the recess. A connector in accordance with the present invention is particularly characterized in that a camming rod is provided on each side of the recess adjacent to the first major surface of the housing. Each contact terminal is fixed to the housing at a fulcrum location adjacent to the second major surface, the contact portion of each terminal being adjacent to the first major surface. The contact terminals normally extend from the fulcrum locations partially into the recess so that the contact portions are normally in the recess. Each contact terminal has an end portion which extends laterally from the contact portion away from the recess and towards the associated sidewall, the end portion being between the first major surface and the associated camming rod. Cooperating camming means are provided on the end portions of the contact terminals and on the associated camming rod, the camming means being effective during movement in one direction to flex the terminals inwardly of their respective cavities so that the contact portions move from the recess into the cavities to permit insertion of the circuit board under ZIF conditions. Upon movement of the camming rods in the reverse direction, the opposite direction from the first direction, the terminals return towards their normal positions and the contact portions are resiliently biased against the conductors on the circuit board.
In accordance with a further embodiment, the end section of each contact terminal comprises a bight section and a tip section, the bight section extending past the associated camming rod and towards the adjacent housing sidewall and the tip section extending transversely of the bight section and being beside, and generally parallel to, the associated sidewall. The tip section and the bight section partially surround the associated camming rod and the camming means are on the tip section and on the adjacent portions of the camming rod.
In accordance with a further embodiment, on each side of the trough-like recess, alternate contact terminals have their contact portions closer to the first major surface of the housing than the contact portions of the remaining contact terminals so that the connector can be used with a panel-like member having conductors on staggered centers.
In accordance with further embodiments, the contact terminals are flat stamped members and the trough-like recess extends to, and intersects, at least one of the endwalls of the housing. In accordance with further embodiments, the camming rods are rotatable cylinders having chordal surface portions in alignment with each contact terminal and the camming rods are metallic rods provided with insulating coatings.
In accordance with further embodiments, the connector is intended for use with a circuit board having conductors on only one surface thereof, the connector having only one row of contact terminals instead of two rows.